/Engine/Source/Runtime/Engine/Classes/Engine/StreamableManager.h
Blocks until the requested assets have loaded. This pushes the requested asset to the top of the priority list, but does not flush all async loading, usually resulting in faster completion than a LoadObject call
[EAsyncPackageState::Type](API\Runtime\CoreUObject\UObject\EAsyncPackageState__Type) WaitUntilComplete ( float Timeout, bool bStartStalledHandles )